1. Field of the Invention
The present invention relates to an ink set comprising at least inks of the three colors yellow, magenta and cyan, special inks of colors other than these three colors, and a reaction liquid containing a reactant, and more particularly to a pigment ink set and an ink jet recording method using this pigment ink set.
2. Description of the Related Art
Pigment inks are generally superior to dye inks in terms of the image fastness of printed articles, and are used in various applications that utilize this characteristic, for example as inks for wide format color ink jet recording aimed at the sign and display markets. In such color ink jet recording, normally a variety of hues are rendered by using a 3-color ink set comprising water-based pigment inks of the three colors yellow (Y), magenta (M) and cyan (C), which are the three primary colors for subtractive colormixing, or else a 4-color ink set in which black (K) is added to this 3-color ink set. Moreover, as ink sets having a broader color reproduction range than such 3-color and 4-color ink sets, ink sets have been proposed that contain water-based inks of colors such as orange and green in addition to the YMCK inks.
Moreover, with regard to improving the ink jet recording method using such a conventional ink set, an ink jet recording method in which a reaction liquid containing a reactant that acts to agglomerate the inks is used, i.e. a so-called two-liquid (inks plus reaction liquid) ink jet recording method, is known (see, for example, Japanese Patent Application Laid-open No. H9-286940, Japanese Patent Application Laid-open No. H10-120956 and International Patent Application Publication No. WO 99/05230). According to this two-liquid ink jet recording method, through the reaction liquid and an ink coming into contact with one another on a recording medium, the reaction liquid breaks down the dispersed state of an ink component such as a pigment, thus agglomerating the ink component to form an agglomerate on the recording medium, and hence a high-quality printed article with high color density and little blotting or unevenness can be obtained. With this two-liquid ink jet recording method, adequate coloring can be realized with regular paper, for which conventional ink jet recording methods have been inadequate, and hence the two-liquid ink jet recording method is particularly effective in the case that regular paper is used as the recording medium.
With the two-liquid ink jet recording method used up to now, a water-based reaction liquid is fired onto the recording medium in addition to the water-based inks, and hence the amount of water-based liquid fired onto the recording medium per unit area is greater than in the case of an ink jet recording method using a regular ink set not containing the reaction liquid. However, regular paper used as the recording medium is such that if a large amount of water comes into contact therewith, then hydrogen bonds between the cellulose fibers are broken at the parts where the water contacts the paper, and hence expansion occurs at these parts, causing deformation such as wrinkling. There has thus been a problem that, in the case that regular paper is used as the recording medium, the two-liquid ink jet recording method described above causes deformation such as wrinkling of the regular paper. The wrinkling becomes worse in particular at printed parts of secondary or higher order colors (mixed color parts) where the ink firing amount is high, greatly reducing the image quality of the printed article. The problem of wrinkling can be resolved by reducing the firing amount of the inks and the reaction liquid, but if the firing amount is reduced then the coloring ability drops.
It is thus an object of the present invention to provide an ink set and an ink jet recording method using the ink set, according to which a high-quality printed article can be provided for which deformation such as wrinkling does not occur, the color density is high, and there is little blotting or unevenness even if regular paper is used as the recording medium.
The present inventors carried out various studies into an ink jet recording method using an ink set comprising pigment inks of the three colors yellow, magenta and cyan and a reaction liquid containing a reactant, i.e. the so-called two-liquid ink jet recording method, and as a result discovered that if a pigment ink set is used that further comprises, in addition to the above, as special inks two pigment inks that have a hue angle ∠Hxc2x0 as defined in CIELAB color space on a recording medium in a specified range, then when forming mixed color parts of secondary or higher order colors, due to using the special inks, characters and/or images with high coloring can be formed without firing a large amount of the inks, which would cause wrinkling with regular paper.
The present invention is based on the above finding, and attains the above object by providing an ink set comprising at least: inks of three colors, that is a yellow ink having a hue angle ∠Hxc2x0 as defined in CIELAB color space on a recording medium in a range of approximately 80xc2x0 to approximately 110xc2x0, a magenta ink having the above-mentioned hue angle ∠Hxc2x0 in a range of approximately 330xc2x0 to approximately 360xc2x0, and a cyan ink having the above-mentioned hue angle ∠Hxc2x0 in a range of approximately 230xc2x0 to approximately 260xc2x0; undermentioned ink (A) and/or undermentioned ink (B); and a reaction liquid containing a reactant.
Ink (A): An ink having the above-mentioned hue angle ∠Hxc2x0 in a range of approximately 0xc2x0 to approximately 80xc2x0.
Ink (B): An ink having the above-mentioned hue angle ∠Hxc2x0 in a range of approximately 260xc2x0 to approximately 330xc2x0.
[The above-mentioned hue angle ∠Hxc2x0 is tanxe2x88x921(b*/a*)+180xc2x0 in the case that a* less than 0 and tanxe2x88x921(b*/a*)+360xc2x0 in the case that a* greater than 0. a* and b* represent the perceived chromaticity indices as defined in CIELAB color space.]
Note that in the present invention, a glossy recording medium such as PM photographic paper (made by Seiko Epson Corporation) is used as the xe2x80x98recording mediumxe2x80x99 when xe2x80x98CIELAB color space on a recording mediumxe2x80x99 is mentioned.
Moreover, the present invention provides an ink set comprising: a yellow ink having an absorption spectrum with an absorption area over 400 nm to 500 nm in a range of 30 absxc2x7nm to 350 absxc2x7nm; a magenta ink having an absorption spectrum with an absorption area over 500 nm to 600 nm in a range of 20 absxc2x7nm to 200 absxc2x7nm; a cyan ink having an absorption spectrum with an absorption area over 600 nm to 700 nm in a range of 50 absxc2x7nm to 400 absxc2x7nm; undermentioned ink (A) and/or undermentioned ink (B); and a reaction liquid containing a reactant.
Ink (A): An ink having an absorption area over 500 nm to 600 nm equal to or greater than the absorption area over 500 nm to 600 nm of the above-mentioned magenta ink.
Ink (B): An ink having an absorption area over 500 nm to 600 nm equal to or greater than the absorption area over 600 nm to 700 nm of the above-mentioned cyan ink.
Moreover, the present invention provides an ink set comprising: a yellow ink having an absorption spectrum with an absorption area over 400 nm to 500 nm in a range of 30 absxc2x7nm to 350 absxc2x7nm; a magenta ink having an absorption spectrum with an absorption area over 500 nm to 600 nm in a range of 20 absxc2x7nm to 200 absxc2x7nm; a cyan ink having an absorption spectrum with an absorption area over 600 nm to 700 nm in a range of 50 absxc2x7nm to 400 absxc2x7nm; undermentioned ink (A) and/or undermentioned ink (B); and a reaction liquid containing a reactant.
Ink (A): An ink such that the absorption area over 400 nm to 500 nm of ink (A) is in a range of 0.5 times to 2.0 times the absorption area over 500 nm to 600 nm of ink (A).
Ink (B): An ink such that the absorption area over 500 nm to 600 nm of ink (B) is in a range of 0.5 times to 5.0 times the absorption area over 600 nm to 700 nm of ink (B).
Moreover, the present invention attains the above object by providing an ink jet recording method of forming characters and/or images on a recording medium using an ink set as described above.
Moreover, the present invention attains the above object by providing an ink jet recording method of forming characters and/or images on a recording medium using an ink set as described above, wherein droplets of the inks and the reaction liquid are discharged such that the inks and the reaction liquid come into contact with one another on the recording medium, and in the case of forming mixed color parts of one or more colors on the recording medium by mixing droplets of a plurality of the inks on the recording medium, at least one of the inks other than the ink (A) and the ink (B), and the ink (A) and/or the ink (B) are used.
Moreover, the present invention provides a recorded article on which characters and/or images have been formed using an ink jet recording method as described above.